Technical Field
The present invention relates to superconductor qubits, and more particularly to devices and methods for tuning qubit frequencies using a laser technology.
Description of the Related Art
Superconducting quantum bits (qubits) show great promise for quantum computing, with ever-increasing coherence times combined with the possibility of standard semiconductor fabrication methods leading to visions of a useful quantum computer. However, one outstanding problem is in the control of qubit frequencies. For example, operation in a surface code implementation requires control of fabricated qubit frequencies to permit gate operation on a lattice. A minimum of at least five distinct frequencies is required. In addition, to reduce drive electronics complexity, it is desirable to control frequency distributions of nominally identical qubits to within a known tolerance.
The observed spread in Josephson junction critical currents is in the range of 10% standard deviation depending on junction size, corresponding to ˜5% spread in qubit frequency. Despite decades of research into fabrication and control of Josephson junctions, no significant improvement has been seen in the spread observed. Similar spreads are observed in other oxide junction technologies such as magnetic memory (MRAM), indicating that this may be an intrinsic property of such devices.
Qubit frequencies need to be controlled, and the fabrication process typically used for devices results in a spread of frequencies which is insufficient for application in a large scale quantum computer.